Move update-nixpkgs / diff-closures docs to proper place

docs/dev/README.rst

@@ -56,6 +56,17 @@ That will update ``nixpkgs.json`` to the latest release on the nixos release cha
 To update the channel, the script will need to be updated,
 along with the filenames that have the channel in them.
 
+To create a text summary of what an update changes - to put in Merge Requests, for example - run:
+
+.. code: shell
+
+    nix-build -A morph -o result-before
+    update-nixpkgs
+    nix-build -A morph -o result-after
+    nix-shell -p nixUnstable
+    nix --extra-experimental-features nix-command store diff-closures ./result-before/ ./result-after/
+
+
 Gitlab Repositories
 ```````````````````
 To update the version of packages we import from gitlab, run:

tools/update-nixpkgs.rst

-To create a nice summary text to of what an update will change - to put in Merge Requests, for example - run::
-
-    nix-build -A morph -o result-before
-    update-nixpkgs
-    nix-build -A morph -o result-after
-    nix-shell -p nixUnstable
-    nix --extra-experimental-features nix-command store diff-closures ./result-before/ ./result-after/
-